Why do my phone feel worse after updating to android 12?

After upgrading my g21 to androind 12 Here are some of the fixes that should be done.

1. My phone can Stay on the charger showing its charging but actually not charging at all.

2. Some streaming apps like showmax scramble my touch screen and shrinks the phones window to 3/4 of the screen.

3. Most apps keep crashing but the system ui and dialer crashes every 1 out 2 times.

4. My phone feels slower than ever.

Kindly share a security patch ASAP.